Hi I have got 4 Hibiscus plants/trees in my garden all in relative same type/ spots. (South facing against a fence) three are in good condition but one (in the middle) has only just started to leaf. The others have started to leaf a month or two ago! Last year this same plant had very few flowers! Would appreciate any ideas whether this is a bug or disease!
Try Nitrogen based fertilizer. Nitrogen promotes healthy foliage. Once the plant has leaves, give phosphorous fertilizer which enhances root systems and flower production.